The chemical name for olmesartan medoxomil is 4-(1-hydroxy-1-methylethyl)-2-propyl-1-[[2′-(1H-tetrazol-5-yl)[1,1′-biphenyl]-4-yl]methyl]-1H-imidazole-5-carboxylic acid (5-methyl-2-oxo-1,3-dioxol-4-yl)methyl ester (Merck Index 13th ed.).
The chemical structure of olmesartan medoxomil is:

The empirical formula is C29H30N6O6.
The molecular weight is 558.58.
Olmesartan medoxomil is a prodrug that is hydrolyzed during absorption, and it is a selective AT1 subtype angiotensin II receptor antagonist. Olmesartan medoxomil is disclosed by U.S. Pat. No. 5,616,599 to Yanagisawa et al. It is marketed as BENICAR® in film-coated tablets of 5 mg, 20 mg, and 40 mg for treatment of hypertension in a human.
The synthesis of olmesartan medoxomil (OLM-Mod) per se is illustrated as follows (see also Annu. Rep. Sankyo Res. Lab 2003, 55, 1-91):

The prior art synthetic methods focus on the coupling between the substituted imidazole and the substituted biphenyl methylene bromide. Additional synthetic methods for these olmesartan medoxomil intermediates are described by: JP 11302260, JP 11292851, JP 07053489, JP 06298683, U.S. Pat. No. 5,621,134, EP 838458, DE 19757995, U.S. Pat. No. 6,111,114, and U.S. Pat. No. 6,214,999.
Step (vi) (the deprotection step) of the prior art synthesis is illustrated as follows:

Example 61(b) of the '599 patent discloses a process for preparing crude olmesartan medoxomil from a mixture of trityl olmesartan medoxomil (MTT) and aqueous acetic acid. Col. 176, lines 24-37. Triphenyl carbinol (TPC) is removed, and olmesartan medoxomil is isolated by evaporation.

Because of the acidic conditions and the presence of water, the impurity OLM-acid is also formed during the reaction by hydrolysis of the ester bond. The prior art process yields crude olmesartan medoxomil containing 2.2% OLM-acid per area percent HPLC.
There is a need for improved processes for preparing olmesartan medoxomil.